The present invention relates to a method for piecing a yarn in a spinning rotor of an open end spinning device, where after the yarn is re-introduced into the spinning rotor, the supply of fibers to the spinning rotor commences, a well as a device for effecting the method.
Attempts have repeatedly been made to improve the yarn piecers in open end spinning by varying the sequence of yarn return and the start of fiber supply. Thus, for example, it is known initially to feed fibers to the spinning rotor and then to feed the yarn back into the spinning rotor (DE-OS 2 505 943). In this way the yarn end fed back into the spinning rotor is deposited upon a fiber ring already present and into which the torsion imparted to the yarn end can be transferred so that the fiber ring can be exploded and the yarn end can be tied in. Since the torsional movement of the transferable yarn end is limited, it is possible to work only with limited fiber supply. However, this results in a weak or thin point in the yarn in the area of the yarn piecer.
In order to eliminate the difficulties encountered during exploding of the fiber ring, it is already known to cut off the fiber tuft arranged in the area of the fiber opening roll prior to piecing, and to lead off the fibers thus severed and to build up the fiber ring formed in the spinning rotor from the shortened fibers prior to returning the yarn end into the spinning rotor. (DE-OS 2 507 153). Such a fiber ring can be very easily exploded since the fiber ring has only very limited strength. However, since here too the fiber ring is exploded, it cannot contribute towards strengthening the yarn piecing achieved in this manner.
It is also known to commence the fiber supply only after the yarn is returned (DE-OS 1 560 298).
However, since the yarn is allowed to remain in the fiber collecting channel for only a very short period of time, and since otherwise there is a danger of the fibers becoming severed by twisting, only relatively few fibers can be fed into the spinning rotor, so that by this manner too a weak point will appear in the piecing area.
It is therefore the object of the present invention to provide a method and an apparatus for producing relatively short piecing regions in the yarn with sufficient strength and the smallest number of variations from the normal yarn strength.